In electrophotographic processes requiring an image cylinder and a blanket cylinder to produce electrophotographic copies, the image cylinder typically receives a charge, an image and a toner coating on the image area and then transfers the toner image to a blanket cylinder. The blanket cylinder transfers the toner image to a substrate, such as paper or the like, which passes via a web between the blanket cylinder and a back pressure roller to transfer the toner image to the substrate with the substrate thereafter being fused, as well known to the art.
In such processes, the image cylinder has a cylinder that typically includes a mandrel that may be of aluminum, steel or any other suitable and durable metal or conductive plastic of a suitable thickness to produce a non-compliant member that may be about 10 millimeters (mm) in thickness. The mandrel may include reinforcing structure internally and includes a very smooth, low out-of-round tolerance exterior.
The image cylinder includes a mandrel and a sleeve positioned over the outside of the mandrel and is used for production and transfer of the images to the blanket cylinder. The mandrel also includes bearings connected to each of its ends for positioning in an electrophotographic machine and has an air inlet into an interior of the mandrel for an air discharge to a plurality of holes placed around one end of the mandrel near a tapered end of the mandrel.
The blanket cylinder has a cylinder that typically includes a mandrel that may be of aluminum, steel or any other suitably durable metal or conductive plastic of a suitable thickness to produce a non-compliant member that may be about 10 mm in thickness. The blanket cylinder includes a mandrel and a sleeve positioned over the outside of the mandrel and is used for transfer of images from the blanket cylinder to a substrate.
The mandrel may include reinforcing structure internally and includes a very smooth, low out-of-round tolerance exterior. The mandrel also includes bearings connected to each of its ends for positioning in an electrophotographic copying machine and has an air inlet into an interior of the mandrel for an air discharge through a plurality of holes placed around one end of the mandrel near a tapered end of the mandrel.
The sleeves have been produced by the use of a metal core, which is typically a non-compliant metal member, such as aluminum, nickel, or the like, that may be produced by plating, extrusion or the like.
The production of metal cores by plating or the like has been found to be expensive and difficult to control sufficiently to produce a metal core of uniform thickness without nodules, voids or the like. While desirable cores have been produced in this manner, it is expensive and difficult to dependably produce high quality metal cores. In an alternate process, extrudates such as aluminum may be used. Such extrudates have a relatively constant internal diameter but the surface is relatively uneven for the purposes for which the metal cores are used. It has been found that such aluminum extrudates can be placed on a mandrel with an interference fit and machined to have a desired outside diameter and finish.
It has also been found, in the use of such cores, that if scratches or other defects occur on the core inside diameter during mounting or while on the mandrel it renders the installation and demounting of the mandrel with an interference fit by the air step method to be very difficult if not impossible. Further, such variations can result in difficulty in producing an exterior surface of the desired diameter and finish. It has also been found that when the core is placed on a mandrel with an interference fit in many instances the metal, such as aluminum, tends to gall, i.e., suffer extensive abrasive wear and deposit quantities of the inner surface of the aluminum extrudate on the exterior of the mandrel. Both of these events are very undesirable and result in a loss of tolerance control both on the exterior of the mandrel and the inside of the extrudate. Even if the outside of the extrudate as mounted on the mandrel has been machined to the desired diameter and tolerance, the loss of metal to the surface of the mandrel may result in an unacceptable variation in the outer diameter when the core produced from the extrudate is placed on another mandrel.
Since the use of metal extrudates allows the production of metal cores for the blanket cylinder and image cylinder sleeves much more economically, a method has been sought by which these difficulties and others can be obviated and metal cores having the desired tolerance produced more dependably from aluminum extrudates.